I haven’t researched whether this has changed, in 15.10, or whether it has been this way since ubuntu switched to systemd, which is probably the case.
Under systemd, ubuntu no longer uses the /etc/init.d/mysql script, but instead uses a systemd unit in /lib/systemd/system/mysql.service which invokes /usr/bin/mysqld_safe to start and stop mysqld.
I have had a lot of trouble with this, and had to do a lot of debugging to figure out what is going on. Probably I would not have had trouble if I were not trying to port over a running mysql installation manually, i.e. if I just installed mysql-server and proceeded to create new databases, new entries in mysql etc.
One issue is that a mysql install creates a file in /etc/mysql called debian.cnf which contains a user/password for user debian-sys-maint with a generated password, and this is put into the mysql users table, to enable various operations to be performed by mysqladmin using these credentials.
The first problem was that when I copied over the mysql table from the previous installation, I was copying in the old password for debian-sys-main, which didn’t match the debian.cnf file which was installed when I did the apt-get install mysql-server. So I had to read the debian.cnf file, extract the password and change the password in the mysql table.
Continue reading MYSQL on Ubuntu 15.10